System of connections for multiphase choking coils



A. GAUDENZI Janes, 1923. 1,457,359

sYs'I-Eu or commcrlous PQR nirwxruxsa cncxnm corna Filed Aug. 29. 1921Patented .lune 5, 1923.

- UNITED STATES um GAUDENZI, F BADEN, SWITZERLAND, ASSIGNB TOAKTIENGEBELLSCHAIT BOVEBI CIE.,.0F BADEN, SWITZERLAND.

or coimncrroivs ron nnL'rxPmsa Cuomo come.

hpnum nea mgm ze, im. serial no. 496Mo.

i .citizen of the swiss Republic and residing n No. 7Martinshergstrasse, eden, Switzer- V I land, have'invented certain newand useful lio Improvements in the S s of Connections '01' MultiphaseChoking Coils (for which I ave filed applications 1n Germany Nov. 28,1917; Switzerland Nov. 19, 1918; France Nov.. 19, 1918; Italy Nov. 27,1918; Austria Nov.'14, 1918),of which'the following is a specification.

In order to generate by means yof. mercu vapour rectifiers a directcurrent whichvwi l be as free as possible from higher harmonics, it isusual to increase the number of phases of the generating alternatingcurrent and to supply a plurality of anodes with this multiphasecurrent, the said anodes corres onding to the number of'phases or to awho e muitiple thereof. Now in the case of large outputs it is necessaryto connect several vapour gaps of the sume phase in parallel, this Beingeffected in the same container or by connecting a number of rectifiersin parallel. In order to obtain at the same time reliableV oper- -ationin parallel of the vapour gaps of `the same phase, it has been roposedto interpose ohmic or better still in uctive resistances in l theindividual anode circuits of the rectifier.

These resistances have hitherto been mainly constructed parately foreach lanode in the form of single phase chokin coils. It is naturallymore practicable owever if a multiphase choking coil be provided' havinga. number of limbs with a`n iron core of lthe simplest possibleconstruction.

In order to obtain the least possible drop in voltage in th'e directcurrent circuit, it has been proved .theoretically and b experiment tobe preferable to-cause the fiel fluctuations in the iron core'of thechoking coil to have as nearly as possible a sine form. This problem inconnection withchokincf coils for rectifier operation is different fromthat of other choking coils, because as is well known, the circuits ofthe individual anodes connect ed to different alternating current phasesonl carry current during a fraction of the periods of the alternatingcurrent supplied to them. Then the number of phases is greater thanthree as is 'usual in the operaf tion of rectifiers, for practicalreasons, the' windings of at least two phases will be mounted on eachlimb of the multi.column iron core of the choking coil.

The present invention relates toian arran ement of this type. v

T e new system of connections accordingly' relates to niultiphasechoking coils having a common iron core and the coils of at least twodifferent phas on each column for the operation of rectiiers, andconsists in connecting the parts ofthe choking coil winding in such amanner that -the coils situated on a column will either individually orin groups produce magnetic fluxes in opposed directions in this columnin a manner which has already been roposed in German patentspecification i o. 238,754, more particularlv for coils of the. samephase mounted on each limb, so that the magnetic flux produced in thesume column by coils of the other columns immediately before and afterits own imsgnetiziitio has the same direction as, but

smaller ordinates than, the ux induced by its own coils. By this meansthe time course of thf` magnetic flux in cach column will vbeapproximately in the form of a sine function. l

Fig. 1 is a diagrammatic view of the improved system df connections formultipliase choking coils showing the manner in which the individualwindings of the choking coil must he connected up so as to produce thefield distribution for a rectifier supplied with six phase current.

Fig, 2 is a diagram of the flux distribution curve. p

Referring to the drawings, a, represents the six phase secondary portionof the cur rent supplying transformer, the said secondary beingconnected in star; b is the choking coil and c the rectifier which sendsdirect current into the mains l- The six secondary terminals of thetransformer a -are designated 1 to 6, the co ending su: :modes of therectifier 1' to 6'; tween these mounted on an iron'core havinthreecolumns d, e, f, are the six windings gto VI of the choking coil b. Themanner in which these coils have to be connected up will he deduced fromthe ilux distribution curve shown in Figure 2. The full line curve reresents approximately thevtime course of this magnetic power flux in thecolumn d 0f the Veis tvely by the coil I. The fundamental lwave of sineform is superposed in a broken line.

As already mentioned, each coil carries current only during the sixthart of a period, and owing to the action o the rect'i er field variationwhich `In order to obtain a ssible of sine orm,`the

will be as nearly as :coil IV, which is situated on the same column d'as the coil I and supplied from the phase 4 of the transformer a whichis displaced by 180, is connected up at the choking' coil in theopposite way to the coil vI so that the maximum field displaced by 180will be negative so as to correspond to the sine course. .The two-sixthsof the curve which in point of time are adjacent the sixth I of thecurve, and which are produced byY the currents in the coils Il and VI ofthe phases 2 and 6 whichV are in advance and beind, respectively, by609, have ordinates of onlyl about half the size ofthe sixth I of thecurve, because the power fluxes induced in the columns'e and f at theluoment are closed through two columns (d und f, (l and c,respectively), so that only half the power flux passes through thecolumn d under consideritiomh h h ort e ur ose o a roac in\r t e sineform, the piirtspll and ylpof theciirve must at the same time bepositive` that is to say, must extend in the direction of the arrowmarked in the coil l. The coil Il must therefore generate beforehand inthe column c a iux which has the direction ofthe arrow marked on it7while afterwards a linx must be produced 1n the same direction from thecoil VI in the column f; both are therefore so connected up (tliesaxnesense of winding being presumed for all the coils) that the currentflows in the opposite direction to that in coil I. lf the same`reasoning is adopted for the remaining coils V and III,

inzage then the connections to the transformer a. shown in Figure l.will be the result.

From the foregoing it will be evident that in the case of choking coilsaccording to this invention, the coil which magnetizes the iron corewill from phase to phase be on a different column, and at the same timethe lthis current is always in the same direction.

direction of the current'in the coils-when 'the sense of winding is thesame--n'ill at the same time alter from one phase to the next following.The new system f connections may also beused with advantage in connection with regulating vchoking-coils and inductive regulators foroperating rectiters.

4Having now described my invention what I claim as new and desire tosecure ters Patent is:-

1. In'a system of connections for multiphase chokm coils havingavcomrnon iron core provide with columns and the coils.of at least twodifferent phases on each column` for the operation of rectifiers, thecombina;- tion that the coils situated on a column produce thereineither individually or ingroups magnetic fluxes inl op ed directions andby Let-4 the magnetic flux pro need in this column by coils of the othercolumns immediately before and after its own magnetization has the samedirection as but smaller ordinates than to phase situated on a differentcolumn andlv at the same time the direction of current flowing in thesecoilswhen the sense of winding is the samelikewise alters from one phaseto the next following.

In testimony whereof I have signed my name to this specification.

4 ARTHUR GAUDENZI.

